1. Field of the Invention
The invention relates to the processing of signals including the use of several digital filters having substantially homothetic templates, especially in the context of analog/digital and digital/analog conversions of signals capable of exhibiting different transmission specifications.
2. Description of the Related Art
The invention applies particularly but not exclusively to the audio-frequency coding devices which may be used for numerous applications of coding of high-quality voice signals. Such coding devices may be inserted into audio-frequency terminals, such as, for example, a telephone of the hands-free type.
A hand-free telephone includes an analog/digital conversion channel, called sending channel, starting from the microphone and going to the digital data transmission channel, as well as a digital/analog conversion channel, called reception channel, starting from the digital channel towards the loudspeaker of this telephone.
The signals flowing on these analog and digital channels must satisfy predetermined transmission specifications, generally governed by transmission standards, such as the CCITT G722 or CCITT G711 standards. The sending and reception channels of these devices include filterings, the frequency attenuation templates of which are specified on the basis of the transmission standards used. Moreover, the frequency attenuation templates are not identical in sending and in reception for a given standard. Hence it is necessary, in these devices, to provide as many digital filters as necessary frequency templates, which is restrictive from the installation and manufacturing cost point of view.